<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        function func1() {
            document.body.style.backgroundColor = "yellow";
        }
        function myFunction(){
            var x = document.getElementById("myDIV");
            x.style.backgroundColor = "white";
        }
        function myFunction1() {
            var x = document.getElementById("myDIV");
            x.style.backgroundColor = "rgb(59, 57, 57)";
        }
    </script>
    <style>
         #myDIV{
            width: 100%;
            height: 1000px;
            background-color: rgb(73, 141, 67);
        }
        #myDIV1{
            margin-top: 50px;
            width: 100%;
            height: 1000px;
            
        }
    </style>
</head>

<body>
    <button onclick="func1()">护眼模式</button>
    <button onclick="func1()">两眼模式</button>
    <button onclick="myFunction()">白天</button>
    <button onclick="myFunction1()">黑夜</button>

    <div id="myDIV">this is a box 
        <div id="myDIV1">this is a box1</div>
    </div>  
    
      
</body>
</html>